An information processing apparatus and method for processing an input image by comparing a stored background image with the input image to obtain a difference, collating a change in the difference and time of the change with conditions for the occurrence of a periodic event and information as to the time of occurrence of the periodic event, which are previously stored in a storage unit, to determine whether the change in state of the input image is the periodic or a non-periodic movement of an object, and selecting, according to a result of the determination, any one of operations according to the periodic or the non-periodic movement of an object.